Thin clients were once as chained to the corporate desktop as full-blown PCs. But that's changing now as wireless LANs and 3G cellular networks become more common.

Using both types of wireless networks, end users can have a relatively simple, diskless notebook-style or handheld device that connects securely, often via a Web interface, to their full suite of enterprise applications running on centrally managed server farms.

The benefits are extensive:

• Minimal or no application development for mobile computing.
• Data remains on servers, not on clients that can be lost or stolen.
• Software updates are made on a few servers, not on many clients.
• Real-time access to enterprise data for mobile workers.

A number of recent developments, besides better wireless connections, are fueling interest in wireless thin clients. One is the growing use of operating systems tailored for thin-client devices, especially Windows XP Embedded (XPE ). But lightweight Linux variants also are cropping up.

Other developments include: the growing sophistication of display technology; the ease with which a growing number of peripherals can be used by thin clients, via USB and other high-performance interfaces; a new breed of thin clients designed for wireless deployments, including products from HP, Maxspeed, Neoware, Wyse Technology and, most recently, Motion Computing.

Motion executives discovered that some of the healthcare customers for the company's line of tablet PCs, running Windows XP Tablet PC Edition, were configuring the devices as thin clients - with no local data storage - linking to Citrix servers.

"The evolution of wireless nets was now allowing the bandwidth for thin-client sessions to work efficiently," says Peter Hunt, vice president of the value-added products division for the Austin, Texas company. "So we thought of using the existing hardware platform but using Windows XP Embedded as the operating system, freezing the software image of the device into a much smaller footprint and using a flash RAM drive instead of a spinning hard drive."

Motion released the M1400TC Table Client in January, priced at about $1,650. The tablet boasts handwriting support, a wide viewing-angle display screen and a built-in fingerprint reader. It has a 10/100M bit/sec Ethernet interface, a PC Card slot, two USB ports and an 802.11g/b WLAN adapter.

Familiar middleware

If much of the client technology is new, the core middleware components of a wireless thin-client deployment are not. They're the same as those used in conventional thin-client desktops. Citrix Systems is the leader in this area, with its suite of software built around its MetaFrame server Independent Computing Architecture (ICA) protocol for client-to-server communications. The most recent, and renamed, release is Citrix MetaFrame Presentation Server 3.0 . Rivals include Microsoft Windows Server 2003 Terminal Services, Tarantella's Secure Global Desktop, Jetro Platforms' CockpIT and BoostIT, and HOB's HOBlink JWT Java software.

Microsoft Terminal Services runs server-based Windows applications, sharing them with multiple users. Microsoft offers a less-developed rival to ICA called Remote Data Protocol.

Lexington Medical Center, a 292-bed complex in West Columbia, S.C., has rolled about 60 of an eventual 100-plus thin clients that link over a Cisco 802.11g/b WLAN to a suite of nursing, clinical and physician applications. These run on a group of 15 Citrix servers, based on HP ProLiant servers with Windows 2000 and Service Pack 4.